Pressure Sensing Catheter

ABSTRACT

A pressure sensing catheter having a proximal end and a distal end. The proximate end includes one or more leur fittings contiguous with one or more lumens disposed within the catheter, a connector coupled to a signal lead which spans the length of the pressure sensing catheter and a pressure transducer coupled at about a distal end of the pressure sensing catheter. One or more apertures are provided at about the distal end of the pressure sensing catheter to allow infusion of fluids and/or withdrawal of fluid samples contemporaneous with pressure monitoring within a blood vessel. Signals sent from the pressure transducer are converted into vascular pressure units by an electronic monitor coupled to the signal lead connector.

CROSS-REFERENCE TO RELATED APPLICATIONS

This non-provisional application is a national stage patent application and claims priority under 35 U.S.C. §371 from co-pending PCT application PCT/US09/35970 filed Mar. 4, 2009 to a common inventor and assignee. This non-provisional application also claims priority under 35 U.S.C. §119(e) from co-pending provisional patent applications 61/033,810 filed Mar. 5, 2008 entitled “Catheter” and 61/092,623 filed Aug. 28, 2008 entitled “Pressure Sensing Catheter,” both to a common inventor and assignee. Provisional applications 61/033,810 and 61/092,623 are hereby incorporated by reference in their entirety as if fully set forth herein.

FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT

Not Applicable

REFERENCE TO A MICROFICHE APPENDIX

Not Applicable

TECHNICAL FIELD

This application relates to pressure sensing catheters, particularly for infusing and withdrawing of fluids from a blood vessel and for measuring fluid pressures within the blood vessel.

BACKGROUND

Physicians, healthcare professionals, veterinarians and researchers may need to establish central venous vascular access for the purpose of monitoring a patient or subject's central venous pressure (CVP), while simultaneously administering medication, hydration fluids, nutrients, radiologic contrasts, or other fluids. There are numerous clinical indications for blood withdrawal which can be facilitated by a central venous catheter. Knowledge of CVP is useful in the management of several disease states and injuries, including but not limited to shock, acute renal failure, hypotension, congestive heart failure, cerebral trauma, and spinal cord trauma. Infused fluids and many medications have effects on CVP, and the ability to measure these effects is medically indicated. In addition to infusion, there are numerous clinical situations for blood of fluid withdrawal which can be facilitated by a central venous access catheter. These situations include but are not limited to checking blood chemistries, blood counts, pathogen identification and treatment, and determining oxygen saturation in central venous blood samples. In the relevant art, securing central venous vascular access includes catheters placed directly into blood vessels via a direct percutaneous route or via subcutaneously tunneled catheters (e.g., Hickman and Broviac devices). Securing central venous vascular access via direct percutaneous central venous line placement may be achieved by inserting a central venous catheter (CVC) into a larger vein of the neck/subclavian or groin region, or by placing a peripherally inserted central catheter (PICC), which is typically inserted into one of the major veins of an upper or lower extremity. The distal ends of either of these types of catheters are advanced into the largest central veins, generally into the superior vena cava or inferior vena cava. However, there are significant differences that exist between CVCs and PICCs in terms of placement techniques and potential complications. Typically, CVCs are generally placed in large veins (e.g., jugular vein) in or near the patient's neck or groin (e.g., external iliac vein) using the Seldinger technique. While effective, CVC placement is not without risks. These risks include inadvertent arterial puncture, intra-arterial placement, large vessel bleeding which may prove difficult to control, air embolism, cardiac arrhythmias and pneumothorax. As a consequence of these significant risks, CVC placement is almost exclusively performed by a skilled physician, effectively limiting the number of those capable of performing CVC placement.

In the relevant art, CVCs typically employ fluid column manometer transduction of CVP. Fluid column manometry requires skilled personnel and the utilization of one the catheter's lumens (as detailed below), rendering that lumen unavailable for simultaneous use as an infusion or blood drawing port. Due to the need for skilled operators and operator-dependent external equipment required for pressure measurements using this technique, from a practical standpoint CVP measurement is restricted to specialized settings, such as the intensive care unit (ICU) or the operating room (OR). This fact limits the practical applicability of CVCs for measurement of CVP in the ICU/post-OR and post-hospital settings, despite potential continued need for such information to guide care. Moreover, due to issues regarding catheter care and safety, patients are rarely discharged from hospital care to home with a percutaneous CVC still in place.

In current manometer transducer CVP measurement, at least one lumen of the catheter is filled with an isotonic saline solution, and pressure measurements are made using a manometer situated external to the patient. This is typically performed by specially trained staff who must take particular care to position an external transducer at a height approximating the level of the patient's right atrium. Operator-dependent variations in positioning of the external transducer height, or change in patient position after transducer positioning, can predispose to erroneous CVP measurements which can adversely affect care decisions. In addition, the saline solution is in direct contact with biological fluids in a given blood vessel which could provide a direct path for pathogenic organisms resulting in sepsis.

Moreover, the manometer transducer measurement technique is less than ideal for PICC applications, most notably due to the very small diameter of PICCs in general, and the size of the lumen dedicated as a saline column in specific. Kinks, blood clots or other restrictions in the saline pressure column prevent accurate measurement of CVP. Additionally, hydrostatic forces caused by the ratio of the saline pressure column diameter vs. saline column length can additionally introduce error to the measurement of CVP. Reduced-size catheters capable of electronic CVP measurement use a venting lumen to reference an atmospheric reference for pressure measurements. A venting lumen occupies valuable space within the catheter and is not available for infusing or withdrawing fluids. Catheters that use fluid column transduction of CVP do not allow for simultaneous fluid infusion or withdrawal from the CVP measurement lumen during CVP determination.

Existing multi-lumen catheter devices present limitations when bolus infusions are indicated due to semi-rigid septum wall design. Existing designs are not intended to allow the septum wall to undulate or flex under bolus pressure. As a result, movement in the septum wall is largely a function of the elastomeric properties of the catheter material, not the design of the septum wall, and as such is negligible. This semi-rigidity effectively limits instantaneous volume as a bolus travels through the catheter, with a resultant increase in bolus delivery time. The resultant increase in medication or nutrient delivery time can have a negative impact on the patient, particularly the critically ill. Limitations of the maximally achievable flow rate through a given lumen may result in sub-optimal patient care at times of acute clinical need. In addition, conventional luminal design may be predisposed to intra-luminal thrombosis and catheter dysfunction.

The approaches described in this section could be pursued, but are not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.

SUMMARY

In a peripherally-inserted central catheter (PICC) embodiment, an electronic pressure-sensing catheter is provided which is designed to facilitate catheter placement and minimize catheter insertion-related complications (including unintended and undesirable placement or migration of catheter tip into right heart structures) by providing real-time pressure measurement both during and post-insertion. Employment of the electronic pressure-sensing element in the embodiment eliminates need to employ conventional fluid-column manometry technique to determine CVP, thereby freeing a lumen of the catheter for other uses, while simultaneously eliminating inherent shortcomings of fluid column manometry, including introduction of infectious agents via the CVP measurement lumen and operator-dependent error in CVP measurement. In this embodiment, the electronic pressure sensing element is non-operator-dependent and does not require a venting lumen to reference atmospheric pressure, thus providing a significant advantage over existing designs and allowing for a more compact catheter design that minimizes risk of catheter-associated thrombosis of resident vessels compared with comparable larger diameter catheters. In this embodiment, more compact design extends the lower limits of patient anatomic size for which catheter may be employed for CVP determination compared with current comparable designs.

In an embodiment, the pressure sensing catheter includes at least one flexible conduit. In an embodiment, a pressure sensing catheter is provided which is designed to minimize uncontrolled bleeding, embolisms and infections. In addition, the pressure sensing catheter may be installed within a blood vessel of a patient by healthcare professionals other than physicians providing healthcare savings. In an embodiment, the pressure sensing catheter includes at least one flexible conduit which is dimensioned to longitudinally travel within a blood vessel without occluding the blood vessel. The flexible conduit includes a proximal end and a distal end. The distal end of the flexible conduit includes one or more apertures for dispensing therapeutic agents and/or other fluids into the blood vessel. The apertures are disposed near the distal end of the pressure sensing catheter such that infusion or sample withdraw does not interfere with pressure measurements.

In multi-lumen embodiments of the pressure sensing catheter, one or more of the apertures may be used to collect fluid samples from within the blood vessel. In this embodiment, sufficient elasticity is provided by use of selected polymeric materials to allow delivery of the therapeutic agent as a bolus. In such embodiments, the delivery of the bolus may temporarily “borrow” volumes from adjacent lumens to allow the bolus to be infused into the blood vessel. Once the bolus has been delivered, the lumens return to their original shape which allows resumption of a continuous stream of therapeutic or other fluids being infused into the patient. Suitable polymeric construction materials for the lumens and/or conduit include but are not limited to polypropylene, polyethylene, polyurethane, polytetrafluoroethylene, silicone rubber, nylon and combinations thereof.

Pressure sensing is accomplished using a pressure transducer generally having a diameter no greater than 12 French, depending on the age of the patient and condition of the patient's vascular system.

The pressure transducer is coupled at about the distal end of the flexible conduit and is used to measure vascular pressures. In an embodiment, the pressure measurements are based on changes in optical signal characteristics as part of the pressure transducer. In another embodiment, pressure measurements are based on piezoelectric properties of a nano-wire which flexes in response to pressure changes. The pressure transducer is configured to measure fluid pressure when disposed proximate to a predetermined location to be monitored, for example, within a superior vena cava of the patient. In one embodiment, the pressure transducer allows for electrical isolation of the patient from the sensing electronics which minimizes the possibility of electrical shock.

At the proximate end of the flexible conduit, one or more leur connectors are coupled to the flexible conduit to allow for infusion and/or withdrawal of fluid samples. The proximate end also includes an connector which allows for linking the pressure transducer to an electronic monitor which converts signals sent by the pressure transducer into fluid pressure readings.

In an embodiment, at least a portion of the pressure transducer is coaxially encompassed by the flexible conduit. For example, the pressure transducer may be encompassed directly into the polymeric construction of the flexible conduit to form an integral pressure sensing catheter, or longitudinally disposed within a lumen of the pressure sensing catheter.

In an embodiment, at least a portion of the pressure transducer is constructed from a material having at least one electromagnetic property. For example, ferromagnetic material and/or radiographic opacity is provided in the construction of the pressure transducer or catheter material in proximity to the distal end of the flexible conduit. Alternately, or in conjunction with the electromagnetic property, a portion of the pressure transducer or catheter material may be constructed from a material having an acoustically reflective property. The electromagnetic and/or acoustically reflective properties allows a practitioner to accurately determine the location of the distal end of the pressure sensing catheter within the blood vessel to ensure proper placement of the pressure transducer. In an embodiment, the placement of the pressure transducer is within a superior vena cava or inferior vena cava.

In an embodiment, the pressure sensing catheter is routed through a peripheral vein, typically into the superior vena cava. Once positioned within the superior vena cava, pressure sensing, infusion and/or withdrawal of fluid samples may be performed.

In an embodiment, routing of the pressure sensing catheter is accomplished using a guide wire which is inserted into the flexible conduit and positioned in the proper location by the practitioner. Once the end of the guide wire is positioned in the proper vascular location, the flexible conduit is slidably positioned such that the pressure transducer is positioned at or near the end of the guide wire. The guide wire is then removed, leaving the flexible conduit and pressure sensor in the proper location within a given blood vessel. In an embodiment, the guide wire is eliminated by reducing the flexibility of the flexible conduit such that at least the outer circumference allows direct routing within a blood vessel.

In an embodiment, a central venous catheter (CVC) may be configured for placement via a central vein of the neck, subclavian vein or groin vein regions which includes an electronic pressure-sensing element and at least one flexible septum

BRIEF DESCRIPTION OF DRAWINGS

The features and advantages of the invention will become apparent from the following detailed description when considered in conjunction with the accompanying drawings. Where possible, the same reference numerals and characters are used to denote like features, elements, components or portions of the invention. Optional components or feature are generally shown in dashed lines. It is intended that changes and modifications can be made to the described embodiment without departing from the true scope and spirit of the subject invention as generally defined by the claims.

FIG. 1 provides an isometric view of a pressure sensing catheter in accordance with an exemplary embodiment;

FIG. 1A provides a detail plan view of a distal end of a pressure sensing catheter in accordance with an exemplary embodiment;

FIG. 2 provides a plan view of an implementation of a pressure sensing catheter in accordance with an exemplary embodiment;

FIG. 3 provides a detail plan view of an implementation of a pressure sensing catheter in accordance with an exemplary embodiment;

FIG. 4A provides an isometric view of a single lumen pressure sensing catheter in accordance with an exemplary embodiment;

FIG. 4B provides an isometric view of a dual lumen pressure sensing catheter in accordance with an exemplary embodiment;

FIG. 4C provides an isometric view of a triple lumen pressure sensing catheter in accordance with an exemplary embodiment;

FIG. 4D provides a cross section view of a triple lumen pressure sensing catheter in accordance with an exemplary embodiment;

FIG. 5 provides a block diagram of an electronic monitor in accordance with an exemplary embodiment.

DETAILED DESCRIPTION

FIGS. 1, 1A provide an exemplary embodiment of a pressure sensing catheter. In an embodiment, pressure sensing catheter 100 is comprised of a flexible conduit section 105 having dual lumens 110, 115 (FIG. 1A). Each lumen 110, 115 is contiguously connected at a proximal end to a leur connector 130, 135 (FIG. 1A; shown with leur caps installed). Leur connectors 130, 135 allow for the contemporaneous infusion of fluids and/or withdrawal of fluid samples from a patient when pressure sensing catheter 100 is disposed in situ. One skilled in the art will appreciate that other types of connectors known in the relevant art may be used in lieu of the leur connectors 130, 135.

A separate signal lead connector 125 is provided at the proximal end of pressure sensing catheter 100 which facilitates coupling of a signal lead 120 with an electronic monitor 500 (FIG. 5). Signal lead 120 longitudinally extends from signal lead connector 125 to a pressure transducer 160 disposed at about a distal end of pressure sensing catheter 100 and connects with electronic monitor 500 via a sensor interface link 170. The longitudinal placement of signal lead 120 is not critical. For example, signal lead 120 may be integrated with flexible conduit section 105, longitudinally disposed in one of lumens 110, 115, or coupled to an exterior surface of flexible conduit section 105.

In this dual lumen embodiment of pressure sensing catheter 100, apertures 140, 145 provide fluidic continuity with lumens 110, 115 and leur connectors 130, 135. Apertures 140, 145 are dimensioned to allow a uniform infusion flow rate using gravity feed. In an embodiment, the cross-sectional area of apertures 140, 145 is approximately equal to or greater than the cross-sectional area of lumens 110, 115. The actual dimensions of apertures 140, 145 may be varied to allow smaller or greater infusion fluid flow rates by changing the dimensions of apertures 140, 145 accordingly.

In an embodiment, apertures 140, 145 are longitudinally disposed proximate to pressure transducer 160 but longitudinally positioned along flexible conduit section 105 a sufficient distance from pressure transducer 160 to minimize pressure measurement disturbances induced by infusion or withdrawal of fluids via apertures 140, 145. A hemispherical tip 155 may be provided at the distal end of pressure sensing catheter 100 to reduce the amount of force required to move pressure transducer 160 into a predetermined location within a blood vessel. In an embodiment, hemispherical tip 155 is constructed from polytetrafluoroethylene to reduce glide resistance within the blood vessel.

In an embodiment, a portion of pressure transducer 160 includes a material which allows for external detection of the distal end of pressure sensing catheter 100. For example, a ferromagnetic material 150 may be disposed proximate to pressure transducer 160 to provide radiographic opacity, ultrasonic reflectivity and/or magnetic detection. Alternately, polymeric materials used in the construction of pressure sensing catheter 100 may be embedded with metal particles to increase electromagnetic and/or ultrasonic detection properties. The electromagnetic and/or acoustically reflective properties of pressure sensing catheter 100 allows a practitioner to accurately determine the location of at least the distal end of pressure sensing catheter 100 within a given blood vessel.

Once pressure sensing catheter 100 is placed in situ, the patient or subject's CVP is measured via pressure transducer 160. In an embodiment, pressure transducer 160 senses reflected optical signals. Reflected optical signals are returned to electronic monitor 500 via signal lead 120 for processing and conversion to CVP. Suitable optoelectric type pressure transducers are commercially available from FISO Technologies, 500 St-Jean-Baptiste Ave., Suite 195, Québec, QC, G2E 5R9, CANADA and BIOPAC Systems, Inc., 42 Aero Camino, Goleta, Calif. 93117. In another embodiment, pressure transducer 160 utilizes a nano-wire which induces a current flow based on piezoelectric properties. An example of a suitable nano-wire pressure transducer is described in non-patent printed publication, “MIT Technology Review,” “A Nano Pressure Sensor,” by Prachi Patel-Predd dated Mar. 6, 2007. The aforementioned non-patent printed publication is hereby incorporated by reference in its entirety as if fully set forth herein. In either embodiment, flexible conduit section 105 generally has a diameter no greater than 12 French 165, depending on the age of the patient and condition of the patient's vascular system. The diameter of flexible conduit section 105 is chosen to allow positioning within a blood vessel without occlusion of blood flow.

Referring to FIG. 2, an exemplary implementation of a pressure sensing catheter 100 is depicted. In an embodiment, a practitioner selects a venipuncture site, with basilic, cephalic or median cubital veins commonly chosen 205. Alternately, venipuncture sites such as neck/subclavian 235 or groin region 230 may be accessed as well. The desired venipuncture site is prepared for the procedure using standard sterile technique. Vascular access is typically achieved using a cannula (not shown) of appropriate size. Various options for vascular access are possible, including the use of a needle/stylet which incorporates a peelable sheath/cannula arrangement. One skilled in the art will appreciate that various methods are known in the relevant art for obtaining vascular access.

Once vascular access is achieved, pressure sensing catheter 100 is introduced into a selected vein 205 via the previously inserted cannula, and may be advanced over a guide wire 400 (FIGS. 4A, 4B, 4C) or via direct puncture placement. Pressure sensing catheter 100 is then carefully advanced through the selected vein 205 into a desired position, typically the superior vena cava 305 for CVP monitoring.

In an embodiment, the insertion procedure may be guided using real-time pressure data provided by pressure transducer 160 if electronic monitor 500 is connected to signal lead connector 125 (FIG. 1). The location of the distal end of pressure sensing catheter 100 may be verified by use of fluoroscopy, conventional X-ray, ultrasound and/or magnetic signature. Proper placement of pressure sensing catheter 100 in the superior vena cava 305 (FIG. 3) is critical, since intrusion of a catheter or other foreign body into the right atrium 310 of the heart 300 can result in arrhythmias and fatal pericardial tamponade. For example, tips of PICC lines frequently migrate either centrally into a chamber of the heart or migrate peripherally so that the tip of the PICC line is no longer in an ideal position or safe location. If the PICC line migrates centrally, the catheter may be malpositioned and could result in perforation and life-threatening hemorrhage. If the PICC line tip migrates peripherally, the utility of the PICC line can be affected, and the PICC line may need to be replaced. Thus the ability to monitor pressure using a PICC line would aid in identification of PICC line tip migration, since pressures vary depending on where in vascular system a pressure transducer is positioned.

In an embodiment, pressure transducer 160 may used to detect unintended proximity of the distal end of pressure sensing catheter 100 to the right atrium 310 or right cardiac ventricle 315. Following verification of proper pressure sensing catheter 100 placement, CVP monitoring, infusion and/or sample withdrawal may then proceed. For example, a first intravenous fluid source IV1 210 is connected to pressure sensing catheter 100 via leur 135 which allows gravity feed of the fluid contained in IV1 210 to flow through lumen 115 and into the superior vena cava 305 of patient 200. Analogously, a second intravenous fluid source IV2 215 is connected to pressure sensing catheter 100 via leur 130 which allows gravity feed of the fluid contained in IV2 215 to flow through lumen 110 and infuse into the superior vena cava 305 of patient 200 contemporaneously with fluid flow from IV1 210.

When infusing, the fluid travels from the proximal end of pressure sensing catheter 100 through a selected lumen 110 or 115 (FIG. 1A) and exits at the distal end of pressure sensing catheter 100 into the patient's 200 blood vessel through a contiguous aperture 140 or 145. For fluid withdrawal, the proximal end of pressure sensing catheter 100 is connected to either a gravity or negative-displacement source, such as syringe 220. During fluid withdrawal, fluids enter the distal end of pressure sensing catheter 100 via apertures 140 or 145, and travel through respective lumen 110 or 115 into a suitable fluid collection container.

In an embodiment, CVP monitoring is provided by pressure transducer 160 (FIG. 1A) which is positioned within the superior vena cava 305. In this embodiment, optical signals are generated by electronic monitor 500 and sent through signal lead connector 125 (FIG. 1A). Signal lead 120 (FIG. 1A), which in this embodiment is an optical fiber, transfers the signals to pressure transducer 160 which reflects optical signals back to electronic monitor 500 as a function of vascular pressure. Electronic monitor 500 processes the reflected optical signals and converts the processed optical signals into usable pressure measurements which may appear on a display 560 (FIG. 5).

In an embodiment, CVP monitoring is provided by pressure transducer 160 (FIG. 1A) which is likewise positioned within the superior vena cava 305. In this embodiment, electrical signals are generated by pressure transducer 160 (FIG. 1A) and sent through signal lead connector 125 for processing by electronic monitor 500 as a function of vascular pressure. Signal lead 120 (FIG. 1A), in this embodiment is a wire. Electronic monitor 500 processes the electrical signals and converts the processed electronic signals into usable pressure measurements which may appear on a display 560. A bolus of fluid may be injected into one of the IV lines using for example, syringe 220.

In an embodiment, electronic monitor 500 may be programmed to detect CVP changes that are characteristic of an unintended approach to heart 300 (FIG. 3). An acceptable CVP range may be output by electronic monitor 500 to display 560. Deviations detected by electronic monitor 500 outside the acceptable CVP range may be used to trigger a tactile, auditory and/or visual annunciator. Such annunciators may be integrated into electronic monitor 500 and/or may be located remotely (e.g., nursing station). Additionally, electronic monitor 500 may trigger annunciators via wireless means. Alternately, electronic monitor 500 may communicate with annunciators via a computer network.

Referring to FIG. 3, a detail plan view of a pressure sensing catheter 100 positioned within a central venous system of the patient's heart 300 is provided. In an embodiment, the distal end of pressure sensing catheter 100 is positioned within the superior vena cava such that pressure transducer 160 can measure the CVP within the superior vena cava 305. Flexible conduit section 105 of pressure sensing catheter 100 is cannulated within peripheral vein 205 as shown in FIG. 2. As discussed above, placement of pressure sensing catheter 100 within the patient's superior vena cava 305 must be carefully performed to avoid disruption of normal heart function or damage to the heart itself.

FIGS. 4A, 4B and 4C provides cross-sectional views of various embodiments of pressure sensing catheter 100. FIG. 4A provides an exemplary embodiment of a single lumen 110 pressure sensing catheter 100 in which signal lead 120 is axially encompassed paracentrally within flexible conduit section 105 of pressure sensing catheter 100. An exemplary guide wire 400 is shown axially disposed within lumen 110 for positioning of pressure sensing catheter 100 within a selected blood vessel.

FIG. 4B provides an exemplary embodiment of a dual lumen 110 pressure sensing catheter 100 in which signal lead 120 is axially encompassed within flexible conduit section 105 of pressure sensing catheter 100 and disposed subjacent to lumens 110, 115. A septum 410 is provided which separates lumen 110 from lumen 115. Lumens 110, 115 are depicted as having approximately equal cross-sectional areas for illustrative purposes only. One skilled in the art will appreciate that each lumen 110, 115 may be individually dimensioned to meet a particular requirement. In an embodiment, septum 410 may be constructed from a resilient polymeric material to allow for temporary expansion and contraction of a given lumen 110 or 115 due to infusion of a bolus. A more detailed discussion of variable lumen dimensions is provided below with the discussion accompanying FIG. 4D. As discussed above, an exemplary guide wire 400 is shown axially disposed within lumen 110 for positioning of pressure sensing catheter 100 within a selected blood vessel.

FIG. 4C provides an exemplary embodiment of a triple lumen 110 pressure sensing catheter 100 in which signal lead 120 is axially encompassed within the flexible conduit section 105 of pressure sensing catheter 100 and disposed at about an axial centerline of conduit section 105. In this embodiment, three septa 410, 415, 420 are provided which axially separate lumens 110, 115, 405 from one another. As discussed above, the cross-sectional area of each lumen 110, 115, 405 may be varied to meet a particular cannulation need. In addition, the location of each septum 410, 415, 420 may be varied as well. As depicted, each septum 410, 415, 420 divides the cross-sectional area of flexible conduit section 105 into three equal lumens 110, 115, 405 and are radially disposed relative to an axial centerline of flexible conduit section 105 at approximately 120 degrees apart. One or more of septa 410, 415, 420 may be constructed to allow for temporary expansion and contraction of a given lumen 110, 115, 405 due to infusion of a bolus. A more detailed discussion of variable lumen dimensions is provided below with the discussion accompanying FIG. 4D. As also discussed above, an exemplary guide wire 400 is shown axially disposed within lumen 110 for positioning of pressure sensing catheter 100 within a selected blood vessel.

FIG. 4D provides a cross-sectional view of a triple lumen pressure sensing catheter 100 in accordance with an embodiment. In this embodiment, three septa 410, 415, 420 are radially connected to an inner wall of flexible conduit section 105 such that three separate lumens 110, 115, 405 are provided within pressure sensing catheter 100. Septum 410 includes a straight profile, septum 415 has a fanfold shape with a zigzag profile, and a wall thickness that is thinner than the wall thicknesses of flexible conduit section 105 and septum 410. In an embodiment, septum 420 has an S-shaped, wavy, undulating profile and is provided with a wall thickness that is thinner than the wall thicknesses of flexible conduit section 105 and septum 410. The nonlinear profiles and thinner wall thicknesses render septa 415, 420 more flexible than septum 410.

The flexible septum arrangement is applicable to both CVC and PICC designs, and manufacture of the undulating septum multi-lumen catheter begins with sizing the catheter to the intended use. For pediatric applications, catheters outside diameters of 3 to 6 French are common. In adult applications, outside diameters of 4 to 12 French are common. In all applications, typical catheter and septum wall thickness are 0.002 to 0.010 inches. Next, the desired number of lumens is determined, as well as the location of the guidewire opening. Finally, a suitable flexible, elastomeric, biocompatible polymeric material is selected. For example, suitable polymeric materials for constructing pressure sensing catheter 100 and/or septa 410, 415, 420 include but are not limited to polypropylene, polyethylene, polyurethane, polytetrafluoroethylene, silicone rubber, synthetic rubber, nylon and various combinations thereof. In an embodiment, the nonlinear (undulating and/or zigzag) profiles and/or thinner walls render septa 415, 420 more flexible than septum 410.

The added flexibility accommodates a temporary increase in fluid volume (bolus) in multi-lumen catheters. Flexible lumen volumes allow more rapid delivery of life-saving medications such as epinephrine, anti-arrhythmic agents, bicarbonate, dextrose, antibiotics, etc at times of critical need. Flexible lumens also permit rapid bolus infusion of radiologic contrast agents, such as required for computerized tomographic angiography to detect a pulmonary embolism. A smaller size catheter with flexible septae may provide the benefits of a larger one, and may be less likely to induce clot formation in a given vein in which the PICC resides, as the risk of PICC-associated vascular thrombosis increases as catheter French size increases.

In an embodiment, signal lead 120 provides sufficient stiffness to allow positioning of pressure sensing catheter within a given blood vessel which may eliminate the need for guide wire 400 (FIGS. 4A, 4B, 4C).

In an embodiment, manufacturing of a triple lumen pressure sensing catheter 100 is performed using an extrusion process whereby flexible conduit section 105, septum 410, 415, 420 multi-lumen embodiments and signal lead 120 are extruded together in a single operation. The extruded flexible conduit section 105 is then cut to a desired length, followed by coupling of pressure transducer 160 (FIG. 1A) and optional hemispherical tip 155 (FIG. 1A) to the distal end of flexible conduit section 105. At the proximate end of flexible conduit section 105, leur connectors 130, 135 (FIG. 1) may then be coupled to lumens 110, 115 (FIG. 1A) and signal lead connector 125 (FIG. 1A) coupled to signal lead 120 forming pressure sensing catheter 100. One skilled in the art will appreciate that other manufacturing processes may be used in the production of pressure sensing catheter 100. Electronic monitor 500 (FIG. 2) is provided by the vendor supplying pressure transducer 160.

The use of low cost construction materials allows for the one time use of the pressure sensing catheter. A used pressure sensing catheter may be disposed of as medical waste after use.

FIG. 5 provides a block diagram of an electronic monitor in accordance with an exemplary embodiment. In an embodiment, electronic monitor 500 is coupled to pressure sensing catheter 100 via sensor interface link 170. In an embodiment, electronic monitor 500 includes a communications bus 510 or other communication mechanism for communicating information coupled with bus 510, and a processor 505 coupled with bus 510 for processing information. Electronic monitor 500 also includes a main memory 520, such as a random access memory (RAM), flash memory, or other dynamic storage device, coupled to bus 510 for storing information and instructions to be executed by processor 505. Main memory 520 also may be used for storing temporary variables or other intermediate information during execution of instructions to be executed by processor 505.

In an embodiment, processor 505 executes one or more sequences of instructions contained in main memory 520. Such instructions may be read into main memory 520 from a computer-readable medium, such as storage device 525. Execution of the sequences of instructions contained in main memory 520 causes processor 505 to convert signals received from pressure sensing catheter 100 for outputting in a human cognizable format. In alternative embodiments, hard-wired circuitry may be used in place of or in combination with software instructions to convert signals received from pressure sensing catheter 100 for outputting in a human cognizable format. Thus, embodiments are not limited to any specific combination of hardware circuitry and software. Electronic monitor 500 further includes a read only memory (ROM) 515 or other static storage device coupled to bus 510 for storing static information and instructions for processor 505. A storage device 525, and/or removable storage media 535 such as a magnetic disk, flash memory or optical disk may be provided and coupled to bus 510 for storing information and instructions on computer readable media as is discussed below.

Electronic monitor 500 may be coupled via bus 510 to a display 560, such as a cathode ray tube (“CRT”), liquid crystal display (LCD) or other display device for displaying information in human cognizable format to a user of electronic monitor 500. A user interface 555 is provided for communicating information and command selections to processor 505 of electronic monitor 500. User interface 555 is coupled to bus 510 and may include for example, a keyboard, a mouse or other pointing device, and/or a touch-screen sensor coupled to display 560.

A communication interface 550 may be coupled to bus 510 for communicating information and command selections to processor 505. Communications interface 550 may be a conventional serial interface such as an RS-232, RS-422, or a USB interface. Communications interface 550 may also be configured as a network interface for exchanging data with one or more external networked devices over a private or public packet switched network. In an embodiment, communication interface 550 is used to wirelessly connect pressure sensing catheter 100 to sensor interface 540. In some such embodiments, sensor interface link 170 is a wireless network connection.

Pressure sensing catheter 100 is coupled via sensor interface link 170 to a sensor interface 540. Sensor interface 540 provides any necessary digital signal processing, analog to digital conversion, digital to analog conversion, noise discrimination and/or optoelectric isolation for use of Pressure sensing catheter 100 with electronic monitor 500. Sensor interface 540 is coupled to bus 510 and is controlled by processor 505 executing the sequences of instructions contained in main memory 520.

In an embodiment, an alarm circuit 545 is provided which monitors dynamic fluid signals received over bus 510 from sensor interface 540. Alarm circuit 545 is programmed to provide a human cognizable alert if dynamic fluid signals detected by pressure sensing catheter 100 fall outside an allowable range. For example, homeostasis central venous pressure typically falls within a range of about 2-8 mmHg, while pressures associated with the right ventricle of the heart 300 (FIG. 3) typically range between 5-25 mmHg. Thus, to prevent malpositioning pressure sensing catheter 100 too close to the heart 300, an alarm set to annunciate when dynamic fluid signals indicate, for example, a pressure at 20 mmHg. One skilled in the art will appreciate that other alarm setpoints can be established as well.

Additional processing may be provided to distinguish between central venous pressure waveforms from right ventricle waveforms in order to cause alarm circuit 545 to annunciate an alarm. Alarms generated by alarm circuit 545 may be output audibly, visually to display 560 and/or tactilely to an optional vibratory element 570 provided at the proximal end of pressure sensing catheter 100. One skilled in the art will appreciate that the functionality of alarm circuit 545 may be accomplished by firmware, software or a combination of firmware and software executed by processor 505.

The term “computer-readable medium” as used herein refers to any medium that participates in providing instructions to processor 505 for execution. Such a medium may take many forms, including but not limited to, non-volatile media, volatile media, and transmission media. Non-volatile media includes, for example, optical or magnetic disks, such as storage device 510. Volatile media includes dynamic memory, such as main memory 506. Transmission media includes coaxial cables, copper wire and fiber optics, including the wires that comprise bus 510. Transmission media can also take the form of acoustic or light waves, such as those generated during radio wave and infrared data communications.

Common forms of tangible computer-readable media include, for example, a floppy disk, a flexible disk, hard disk, magnetic tape, or any other magnetic medium, a CD-ROM, any other optical medium, punch cards, paper tape, any other physical medium with patterns of holes, a RAM, a PROM, and EPROM, a FLASH-EPROM, any other memory chip or cartridge, a carrier wave as described hereinafter, or any other medium from which a computer can read.

Various forms of computer readable media may be involved in carrying one or more sequences of one or more instructions to processor 505 for execution. For example, the instructions may initially be carried on a magnetic disk of a remote computer. The remote computer can load the instructions into its dynamic memory and send the instructions over a telephone line using a modem. A modem local to electronic monitor 500 can receive the data on the telephone line and use an infrared transmitter to convert the data to an infrared signal. An infrared detector coupled to bus 510 can receive the data carried in the infrared signal and place the data on bus 510. Bus 510 carries the data to main memory 520, from which processor 505 retrieves and executes the instructions. The instructions received by main memory 520 may optionally be stored on storage device 525 either before or after execution by processor 505.

The various embodiments described herein are intended to be merely illustrative of the principles underlying the inventive concept. It is therefore contemplated that various modifications of the disclosed embodiments will, without departing from the inventive spirit and scope, be apparent to persons of ordinary skill in the art. They are not intended to limit the inventive embodiments to any precise form described. In particular, it is contemplated that the various embodiments of the pressure sensing catheter may be used for contemporaneous infusion, fluid sampling, and pressure measurements of spinal, cranial, lymphatic, endocrine systems or other biological fluid systems in which contemporaneous pressure monitoring and infusion/sample are required. No specific limitation is intended to a particular construction material or manufacturing processes are intended or implied. Other variations and inventive embodiments are possible in light of above teachings, and it is not intended that this Detailed Description limit the inventive scope, but rather by the Claims following herein. 

1. A pressure sensing catheter comprising: a flexible conduit having a proximal end, a distal end, and a lumen longitudinally spanning between the proximal and distal ends; the flexible conduit dimensioned to longitudinally travel within a blood vessel of a patient such that the distal end is disposed proximate to a predetermined location within the blood vessel; a pressure transducer coupled to the flexible conduit at about the distal end and external to the lumen, the pressure transducer configured to generate fluid pressure signals when disposed proximate to the predetermined location within the blood vessel; and, an electronic monitor coupled to the pressure transducer configured to process the fluid pressure signals generated by the pressure transducer.
 2. The pressure sensing catheter of claim 1 wherein the flexible conduit is further dimensioned to allow delivery of a therapeutic agent into the blood vessel via the lumen.
 3. The pressure sensing catheter of claim 2 wherein the flexible conduit is constructed from a polymeric material having sufficient elasticity to allow delivery of the therapeutic agent as a bolus or as a continuous stream.
 4. The pressure sensing catheter of claim 1 wherein at least a portion of the pressure transducer is coaxially encompassed by the flexible conduit but separate from the lumen.
 5. The pressure sensing catheter of claim 1 wherein the flexible conduit further includes at least one septum which longitudinally subdivides the lumen into a plurality of lumens.
 6. The pressure sensing catheter of claim 1 wherein the pressure transducer is optically coupled to the electronic monitor.
 7. The pressure sensing catheter of claim 1 wherein the predetermined location is within a superior vena cava or inferior vena cava of the patient.
 8. The pressure sensing catheter of claim 1 wherein at least a portion of the distal end of the flexible conduit or pressure transducer is constructed from a material having a property selected from the group consisting of: an electromagnetic property, a radiographic opacity property, and a acoustically reflective property.
 9. The pressure sensing catheter of claim 1 wherein the blood vessel is a vein.
 10. The pressure sensing catheter of claim 1 wherein the lumen is configured to coaxially receive a guide wire.
 11. The pressure sensing catheter of claim 1 wherein the pressure transducer is one of a nano-wire and optoelectric pressure transducer.
 12. The pressure sensing catheter of claim 7 where the at least one septum is constructed of a polymeric material having sufficient elasticity to allow lateral expansion and contraction of the plurality of lumens.
 13. The pressure sensing catheter of claim 7 wherein at least two of the plurality of lumens are configured to allow simultaneous withdrawal of a fluid sample via one lumen and allow delivery of a therapeutic agent via a second lumen.
 14. The pressure sensing catheter of claim 1 wherein the flexible conduit is configured to allow fluid pressure measurement proximate in time with therapeutic agent delivery or fluid sample withdrawal from the blood vessel of the patient.
 15. The pressure sensing catheter of claim 1 wherein the flexible conduit has a diameter no greater than 12 French. 